Abstract The field of Osteoimmunology was established in 2005 to understand how bone influences immune and hematopoietic cells, as well as how hematopoietic and immune cells influence bone, in clinical conditions like prosthetic joint infection (PJI). However, critical tools and research protocols for discovery, and technologies required to translate discoveries into clinical diagnostics and interventions for osteomyelitis, did not exist at the commencement of our AO Trauma Clinical Priority Program (AO-CPP) 5 years ago. Thus, we assembled a multidisciplinary team of investigators with extensive experience in bone pathology, microbial pathogenesis, immunology, electron microscopy, material science & engineering, infectious disease and orthopaedic surgery, to enable the major advances that serve as the scientific premise of this Center of Research Translation on the Osteoimmunology of Bone Infection (CoRTOBI). Despite these major advances, additional assay and technology development is needed to complete the research projects in this CoRTOBI. Thus, the goals of the Osteoimmunology Research Core are to: 1) provide the CoRTOBI investigators with state-of-the-art research resources that do not exist elsewhere; and 2) develop novel technologies and assays for future osteoimmunology research. Our approaches to achieve these goals are embodied by the following Specific Aims. In Aim 1 we will process the samples and perform all of the electron microscopy on the infected bone and fabricated nanoporous membranes in Project 1; and the ?Trojan horse? macrophages and tissue abscesses in Project 2. In Aim 2 we will generate the array of nanoporous membranes varying in pore sizes to assess the haptotaxis, metamorphic and durotaxis behaviors of S. aureus in vitro, and clone the genes involved as novel antibiotic targets using a candidate gene and TnSeq mutant library screening approach. In Aim 3 we will use our 3D-printing technology to assess novel antibiotic spacers in vivo in Project 1. In Aim 4 we will screen all the sera from the animal studies, and the 300 PJI patients in the AO-CPP registry, using our 14-antigen multiplex Luminex assay, and as technology development, we will add additional S. aureus antigens to our multiplex Luminex assay. In Project 2, we will also generate novel multiplex-Luminex assays for S. epidermidis and S. lugdunensis, and use them to screen sera from mice and PJI patients, as we have done for S. aureus. Finally, in Aim 5 we will establish protocols for screening and cloning antibody-secreting cells (ASC) in whole blood from mice and humans infected with S. aureus. We will also develop reproducible methods to expand and clone anti-S. aureus ASC directly from murine and human blood as new technology in the Core. Importantly, it is also our intent to share our resources with investigators outside of this CoRTOBI, and transport our research platforms to other institutions with a research focus on Staphylococcal infections, and osteomyelitis. !